The Mount Sinabung eruption: Understanding volcanic jargon

Mt. Sinabung

What is the difference between lava and magma?

Magma is molten rock, and exists beneath the Earth’s surface, in the crust. Lava is basically magma that has reached the surface through a volcano vent. So the short answer is that magma becomes lava once it reaches the surface.

Volcanic lightning — apocalyptic displays

Sometimes you will read about, and see pictures of, volcanic lightning. This really is what it sounds like, and is quite awesome. Japan boasts some of the most spectacular examples of volcanic lightning.

Solid materials — tephra and ash

All explosive volcanic eruptions generate tephra. According to the US Geological Survey website, tephra is composed of “fragments of rock that are produced when magma or rock is explosively ejected.” This ejected material varies greatly in size.

Fissure vents

These holes in the ground go by several names: fissure vents, volcanic or eruption fissures, or simply fissures. When underground magma finds its way into a small crack in the Earth’s crust, it can lead to the creation of larger fractures, or fissures. If there is sufficient pressure behind the magma, the fracture expands and reaches the surface.



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Bruno Cooke

UK author/journalist writing about long distance cycle trips, cultural differences and global politics. Visit